As a screen of a television (TV) becomes larger, it is desired to be able to watch a high-definition video. For this reason, ultra-high definition TV (UHDTV) broadcast has been promoted. In Japan, 4K broadcast service utilizing a communication satellite (CS) and an optical line started in 2015, and the broadcast of UHDTV (4K and 8K) by a broadcast satellite (BS) will start in the near future. Therefore, various electronic devices which correspond to 8K broadcast are developed (e.g., Non-Patent Document 1).
Flat panel displays typified by liquid crystal display devices and light-emitting display devices are widely used for displaying videos. Although the transistors used in these display devices are mainly manufactured using silicon semiconductors, attention has been drawn to a technique in which a metal oxide exhibiting semiconductor characteristics is used for transistors instead of a silicon semiconductor in recent years. For example, in Patent Documents 1 and 2, a technique is disclosed in which a transistor manufactured using zinc oxide or an In—Ga—Zn-based oxide as an oxide semiconductor is used as a pixel of a display device.